This invention is directed to apparatus for pyroprocessing of particulate materials here exemplified by calcined lime pebbles such as are produced from limestone heat-processed in a kiln. The invention is not limited to processing of lime pebbles alone, however, since it may be applied to other heat processed particles of matter such as deadburned dolomite, cement, expanded clay or shale, and the like. The term particles as used herein refers to the many forms of such material including large and small pieces, pebbles, granules, broken solids, fragments, clinkers, etc. In this regard, lime particles processed in the apparatus herein described may, for example, range in their size from dust less than 60 mesh to 2 inches in size to much large particles or agglomerates of lime and kiln coating.
Calcining of lime is typically accomplished in a kiln such as a generally horizontal but inclined rotary kiln heated by one or more burners. In rotary and other types of kilns, it is customary to subject the material being processed to flame temperatures in the order of 2800.degree. F. to calcine the limestone charge. The hot lime exiting from the calcining zone is then deposited on top of a generally vertical cooling bed through which cooling air is passed in counterflow relation to the particle flow in the bed to reduce the temperature of the line to a level that permits subsequent conveying, storage and shipment within a reasonable space and a reasonably short time period. Contemporaneously therewith the sensible heat of the hot lime is picked up by the cooling air which is thereafter directed to the kiln as preheated air for combustion.